<!DOCTYPE html>
<html lang="zh-CN">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>focus伪类选择器</title>
    <style>
        input:focus {
            background-color: tomato;
            color: red;
        }
    </style>
</head>

<body>
    <p>
        input:focus { <br>
        &nbsp;&nbsp;&nbsp;&nbsp;background-color: tomato; <br>
        &nbsp;&nbsp;&nbsp;&nbsp;color: red; <br>
        } <br>
    </p>
    <p>
        <input type="text">
        <input type="text">
        <input type="text">
    </p>
</body>

</html>